I may assure you that 1WU is not 1 part. Not even close. You can check it using trial credits with your data.
For example, I just checked that uploading 1.1GB example table(cell_towers with 14 columns) cost me 0.38 write units.
For example, I just checked that uploading 1.1GB example table(cell_towers with 14 columns) cost me 0.38 write units.
Nonetheless you can't insert a-whole-file-and-just-that-file in less than one write.
This doesn't imply to me that each individual INSERT costs 1 WU, but that it could be fractional. I guess it depends on how you read it?
(See https://news.ycombinator.com/item?id=33081099 for the original wording.)